Volume 9 Number 2 August 1995
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ResultsThe number of patients who came from the two villages for interview were 620 of whom only 202 (133 male, 69 female) qualified for clinical and parasitological examinations (Table 2). Of the total participants, 42.6% were settlers from Wollo or other Administrative regions who settled 8 years ago while the rest were indigenous population. The majority of the participants (55% ) were farmers, and students (Table 1). Table 2: Characteristics of subjects examined by age and sex, Gojeb, and Kishe villages, South-Western Ethiopia, March, 1992.
Reactive skin lesions were seen in 48/202 (23.8%) whereas 90/202 (44.6%) had chronic skin lesions from mild to severe forms. No hanging groin was seen though few cases were reported from the nearest health centre. Reactive skin lesions were fairly distributed in all age groups whereas the chronic lesions were commoner with increasing age. Excoriations and dyspigmentation were commoner in males than in females. Other features had equal distribution in both males and females. Nodules were seen in 29/202 (14.4%), the range being 1-6 and mostly found on the pelvic area. Nodules were fcund in all age groups but more in males. Visual impairment was reported in 34/202 (16.8% ) of whom six were identified as cases of ocular oncho (four early choroidoretinitis, one chronic iritis and one punctate keratitis/cataract). Blindness was bbserved in two patients which is attributed to cararact and glaucoma. The overall parasitological prevalence rate was 110/202 (54.5%) (600% Gojeb, and 50% Kishe). The prevalen~ rate in males was 59.4% and 44.9%; in females and no significant difference was observed .({1.>0.05). The community microfilarial load (CMFL) was (the geometric mean microfilarial count) was 17.2 f and 17.1 mf/mg skin snip (14) for Gojeb and Kishe, respectively. The parasitological prevalence and arithmetic mean for Microfilarial Count (MFC) steadily increased with age (Table 4). The microfilarial count (mt) ranged between ° and 382 per mg skin snip out of which 4.1% had a count of 100 mf or more per mg skin snip. However, the arithmetic mean is 16.6 mf/mg skin snip (Table 4). There was no association between severity of reactive skin lesions and microfilarial count (p > 0.05), and between severity of hyperkeratosis and mf count (p > 0.05). On the other hand, a strong association between dyspigmentation and mf count was observed (p < 0.005). DiscussionThis study was carried out in areas with hyperendemic onchocerciasis (Asefa A. , et al. , 1990, unpublished data). The clinical manifestation of the disease is of moderate intensity most probably due to the recent infection of nearly half of the study subjects. Parasitological and clinical measures of the disease increased steadily with age, suggesting that there was little effective immunity within these communities and that infection accumulated with increasing years of exposure. The disease is perceived as a health problem by the minority of the villagers, of whom 46/202 (22.8%) had sought treatment for onchocerciasis. Both clinical manifestations and parasitological findings between our subjects and those of Seyoum et al (13) seem to be different being higher in our case. This could be due to differences in the study methodologies and ecology .The absence of scrotal elephantiasis, and hanging groin in our case may be due to recent infection of the subjects in the two villages (the majority of the subjects settled there eight years ago) or patients with such manifestations did not appear for the examination. The overall prevalence rate is similar to our previous work (54.4% vs 61.2%) despite the fact that the study designs are different (Asefa A. , et al, 1990, unpublished data). The prevalence rate for females is higher than reported from Bebeka Coffee Plantation Enterprise by Seyoum et al ( 13) .This might be because of the. occupational difference between the two study populations. The two cases of blindness are probably attributed to non-onchocercal glaucoma and cataract whereas six cases of the 34 with visual impairment are suspected to be due to ocular onchocerciasis. A survey conducted in southwestern Ethiopia revealed that, of 428 cases of reduced vision, four were attributed to onchocerciasis (26,27). However, that survey was conducted more than a decade ago which may not be representative for the present epidemiological and clinical conditions of onchocerciasis in Ethiopia. In this context, as recommended by Zein & Kloos (27), the role of onchocerciasis in the etiology of blindness in Ethiopia has yet to be determined by conducting a country representative survey. Reactive skin lesions are higher compared to some of the reports from West Africa (15, 16, 17) but chronic skin lesions are lower compared to the same exposure to the disease in our case. However, itching was reported in similar proportion of the study population. According to Anderson (18), microfilarial count of 100 or more per mg skin snip is regarded as heavy infection. In this case, 4 % of the study population showed heavy infection. Therefore, it can safely be concluded that onchocerciasis in the two villages is hyperendemic with mild to moderate intensity . This study has not measured disabilities due to onchocerciasis which indirectly measures productivity of the victims. However, it depicts that onchocerciasis is a health problem of the villagers calling for appropriate intervention. Identification of the responsible vector must be made and their breeding sites located. Furthermore, the annual transmission potential of the vector(s) must be estimated in order to plan an effective intervention programme. Currently, several studies have indicated that treatment with ivermectin (mectizan) has proved to decrease the intensity of infection and clinical symptoms if administered biannually in a single dose. This same treatment scheme is also said to lower the transmission of onchocerciasis if given over several years (19, 20, 21). Duke et al (20) have found that ivermectin was effective in preventing embryogenesis to the microfilarial stage while, at the same time, it caused a slow but steady attrition of the adult worms. In countries like Ethiopia, where other control measures are not feasible, ivermectin may be used both for the control and treatment of onchocerciasis. Table 3: Clinical sings of onchocerciasis and association of mf count with various lesions (N=202)
Table 4: Prevalence and intensity of microfilariae by sex and age group
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